Knit cycle for clothes dryer

ABSTRACT

A knit cycle is provided for clothes dryers to prevent shrinkage caused by excessive drying due to inadertent presetting of the dryer programmer to an excessively dry setting. During an automatic drying cycle, moisture sensing apparatus is employed to stall or interrupt operation of a cycle terminating timer motor. Selection of a knit cycle overrides an incorrect setting by limiting the ability of the moisture sensing apparatus to affect the operation of the timer motor.

United States Patent 1191 Beard, Jr. et al.

I54] KNIT CYCLE FOR CLOTHES DRYER [75] Inventors: William L. Beard, Jr., Benton Harbor; Ronald E. Hahn, St.

Joseph, both of Mich. [73] Assignee: WTiYliiBbkCbi-p, Benton Hafiz Mich.

221 Filed: Dec. 1l,l70

[2l] Appl. No.: 97,242

52 U .S.Cl. ..34/45,34/48,318/483 s1 lnt.Cl ..F26b 13/10 [58] FieldofSearch ..34/45,48;3l8/483 [56] I References Cited UNITED STATES PATENTS 8/ l 965 Smith ..34/45 1/1970 Elders et al... ..34/45 7/1968 Miller eta].

[ Feb. 6, 1973 7/l970 Niewyk et al ..34/45 9/l966 Guenther et al ..34/45 Primary Examiner-Carroll B. Dority, Jr. Att0rney.lames S. Nettleton, Thomas E. Turcotte, Donald W. Thomas, Gene A. Heth, Franklin C. Harter and Robert L. Judd 5 7 ABSTRACT A knit cycle is provided for clothes dryers to prevent shrinkage caused by excessive drying due to inadertent presetting of the dryer programmer to an excessively dry setting. During an automatic drying cycle, moisture sensing apparatus is employed to stall or interrupt operation of a cycle terminating timer motor. Selection of a knit cycle overrides an incorrect setting by limiting the ability of the moisture sensing apparatus to affect the operation of the timer motor.

5 Claims, 6 Drawing Figures 7' HTENIEurm 6 197a 3.714.717 SHEET 10F 2 Fig.1

6 Fig.6

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PATENIEDFEB 6 I973 3,714,717

sum 2 OF 2 I N VENTORS 1 KNIT CYCLE FOR CLOTHES DRYER BACKGROUND OF THE INVENTION 1. Field of the Invention I t This invention relates to control circuits for clothes dryers, and more particularly to dryer control circuits having a cycle to prevent overdrying of knitted garments.

2. Description of the Prior Art Clothes dryers have heretofore been provided with automatic control circuits adapted to terminate the drying cycle when a selected dryness level is detected by moisture sensing apparatus. A dryer control circuit which operates on this principle is disclosed in U.S. Pat. No. 3,522,660 to Alvin J. Elders, which patent is assigned to. the same assignee as the present invention. In the control circuit disclosed by Elders, a moisture sensor isemployed to gate a silicon controlled rectifier, connected in parallel with a timer motor to preclude operation of the timer motor by shunting half wave power around the motor. Circuits of this type are fully capable of satisfactorily drying knitted garments placed SUMMARY OF THE INVENTION It is therefore highly desirable, anda primary object of the present invention, to provide a dryer control circuit which helps prevent overdrying of knitted garmerits although the controller of the dryer may be improperly set at the, beginning of the drying cycle. This objective'is realized by interposinga switch'in series with a moisture sensor or other controlled condition device, to prevent stalling of the timer motor by the sensordevice. In one embodiment of the invention the switch contact is manuallyoperable through the provision of an associated knit cycle selection switch knob located on the control'console-of the'dryer. In another embodiment of :the'inventiona three cycle timer isin-v eluded-in the control circuit foroperating the programmerand the programmer includes av switch contact which is operable to prevent parallel connection of the moisture sensorand the timer motor. A particular. feature of the invention residesin'the one 'of two serially connected thermostat switches in the heater portion of thecontrol circuit. The one thermostat switchv is designed to-open at a lower tempera ture than the, other thermostat switch; therefore, operation. of the second switch contact places the one thermostat switch in series with the other thermostat switch -and-'t he'-he ater during ;the knit cycle sothat the garments are exposed to a lower drying temperature. The

second switchcontact may also be. ganged with the first switch contact for manual operation, or may be provided; as a part of the programmer in an embodiment which includes a three cycle timer.

BRIEF DESCRIPTION OF THE DRAWINGS Otherv objects, featuresand advantages of the invention, its organization, construction and operation, will 50. provision ofa second switch contact in parallel with energizing circuit for a relay winding 31 between the I be best understood from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is an elevational view of a control console for a dryer constructed in accordance with one embodiment of the present invention;

FIG. 2 is a schematic circuit diagram of a dryer control circuit constructed in accordance with one embodiment of the present invention;

FIG. 3 is a graphical illustration of the open and closed conditions of the knit switch of FIG. 2 in normal and knit drying cycles;

' FIG. 4 is a graphical illustration of the sequence of operation of the programmer contacts illustrated in FIG. 2;-

FIG. 5 is a schematic circuit diagram of a dryer control circuit according to another embodiment of the invention; and

FIG. 6 is a graphical illustration of the operation of the programmer contacts of the dryer control circuit illustrated in FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A control console for a dryer, generally referenced 10 in FIG. 1, may be employed in connection with any of "several well-known dryer constructions, such as those disclosed by Miller et al. in U.S. Pat. No. 3,398,465 and Cobb-ct al. in U.S. Pat. No. 3,409,997, both of which patents are assigned to the same assignee as the present invention. The console .10 includes a front, panel II- for mounting a. plurality of control devices including a programmer controller 12 which is rotatably operable to select a desired drying cycle, a push'to start button 13 for initiating operation of the dryer subsequent to selection of the desired dryingcycle, and a knit cycle selection switch 14 which is operable to select the knit cycle option provided by-the present invention.

FIG. 2 illustrates, in schematic diagram form, a control circuit which may be associated with the control console. 10 of FIG. 1. The control circuit comprises a plurality of input terminals L1, N and L2 for connection to a commercial electrical supply as is well-known and practiced in the art. The controller 12 of FIG. I is schematically illustrated in FIG. 2 as being mechanically linked to a timer motor 16 and further by way of a linkage 15, indicating the programmer, to a plurality of contacts 17, 18, l9.and 20. The push to start button 13 is schematically illustrated in FIG. 2 for completing an terminals L1 and N by way of the contact 17 and adoor operated switch 30 which is linked to the access door (not shown) of the dryer. v

. Adrive motor 33, coupled to a tumbling drum (not shown),.is connectable between the input terminals L1 and N by way of the contact 17, a contact 32 associated withthe relay winding 31 and the door switch 30. The timer motor l6 is also connectable between the terminals L1 and N by way of the contact 17, the contact minals L1 and L2 by way of the contact 18, a first thermostat device 37, asecond thermostat device 38, and a switch 40 which is centrifugally operated by the motor 33 by a predetermined speed.

Moisture sensing is provided by apparatus including a sensor assembly 41 having electrodes 42 and 43. The electrode .42 is connected to ground and the electrode 43 is connected to one end of a resistor 44. The other end of the resistor 44 is connected to one terminal of a capacitor 45 and to the anode of a diode 47. The other terminal of the capacitor 45 is connected by way of a resistor 46 to ground and to the anode of a silicon controlled rectifier (SCR) 54. The cathode of diode 47 is connected at a junction point 48 to a resistor 49 and to a resistor 50. The resistor 49 is further connected to a junction point 53 at the cathode of SCR 54, and resister 50 is connected by way of a neon lamp 51 to the gate of SCR 54. Another resistor 52 connects the gate electrode to the junction point 53 and the cathode'of SCR 54. The resistor 55, mentioned above, serves also to connect the junction 53 of the moisture sensing apparatus to the terminal L1.

The control circuit of the dryer is provided with knit cycle selection by way of a switch 56 connected in parallel with the contact and manually operated by the control knob 14. The control knob 14 is further linked to a switch 57 for selectively shunting the thermostat device 38.

' Referring to FIGS. 2, 3 and 4, the control circuit operates as follows. An operatorloads the dryer, closes the access door to close switch 30, rotates the controller 12 to the desired cycle andpresses the push to start button 13, Rotation of the controller 12 closes the contacts 17 and 18. Depression of the push to start button 13 establishes a temporary powering circuit to energize the relay winding 31 by way of the terminal L1,- the contact 17, the contact 13, the winding 31, the door switch 30 and the terminal N. Energization of the winding 31 closes the associated contact 32 to provide a holding path for the winding 31 in shunt with the contacts 13 so that continuity is maintained upon releaseof the push to start button. I

The depression of the push to start button 13 initiates starting ,of the drive motor 33 by way of the terminal Ll, the contact 17, the contacts 13 which are immediately shunted bythe contact 32, the motor winding'35 and the motor winding 34 via a centrifugal motor 16 may be a hysteresis motor which will not operate on half wave voltage; therefore, the timer motor 16 will not advance when wet fabricbridges the sensor electrodes 42 and 43 while the contacts 19 and 20 are closed. As the fabric in the dryer loses moisture and presents a higher resistance across the sensor electrodes 42 and 43, the voltageon the capacitor will increase causing a corresponding decrease in the-voltage from the point 48 to the point 53. As this latter voltage decreases, it will reach a value that is insufficient to sustain operation of the neon lamp 51 and the timer motor 16 will begin to operate and maintain its operation to time the remaining term of the drying cycle. With the type of control thus far described, knit fabrics are in danger of being over dried, especially if 16 whereby closure of the contact 19 and conduction of SCR 54 prevent operation of the timer motor 16. Selection of the knit cycle operation by means of the knob 14, however, opens the contact 56 and renders the stopping of the motor 16 dependent upon closure of contact 20 simultaneously with closure of contact 19 and conduction of SCR 54.

Referring to FIGS. 1, 2, 3 and 4, the circuit operation with controller 12 set on AUTO and selector knob 14 set to KNIT will be as follows:

At the beginning of the drying cycle, timer motor 16 will be energized through contacts 17 and 32 and door switch 30. Since both contacts 56 and 20 are initially open, timer motor 16 cannot be shunted regardless of the moisture content of the fabrics being dried. As shown in FIG. 4, after an initial period of time, contact 20 is closed .by timer motor 16. Concurrently, contact a 19 is closed for a period of time as indicated by the switch 36, the door switch 30 and the terminal N.

tumblesjinthe drum the contact of the wet fabric across the sensor ele'c'trodes 42 and 43 causes the DC voltage developed across the capacitor 45; to be quite small because the capacitor is permitted to discharge to ground through the wet fabric. Accordingly the voltage between the points 48 and 53is sufficient to break down theneon lamp 51. The neon lamp 51 will fire and gatethe'SCR 54 so that power to thetimer motor 16 will be shunted during alternate'half cycles. The timer the capacitor 45 will charge through'switch 17, switch e 32, resistors 55 and '49 and diode 47. As the wet fabric overlapping crosshatched lines in FIG. 4 to the right of the numerals 19 and 20.

With both contacts 19 and 20 closed, the timer motor may be shunted if the moisture level of the fabric being dried is high enough to cause SCR 54 to be conductive.

If the moisture level of the fabrics being dried is high enough to cause SCR 54 to conduct, the timer motor willbe stalled until the fabrics become dry enough to render SCR 5 4 nonconductive, at which time the timer motor will be energized to run out the drying cycle to tennination.

If the fabric being dried has reached a low moisture level at the time contact 20 closes, SCR will not become conductive and the timer motor 16 will simply continue in operation to run out thedrying cycle to termination.

Operation of the knob 14 to the knit cycle position also opens the contact 57 to remove the shunt from the thermostat device 38 and placethat device in series with the heater means 39 and the thermostat device 37.

three cycle timer, AUTO, KNIT and TIMED (SeeFIG,

6), and that the contacts 19, 20, 56 and 57 of FIG. 2 have been replaced by program operated contacts 58 and 59 The operation of the contact 59 has not been indicated in FIG. 6, but its condition of operation would preferably be closed during the entire AUTO and TIMED cycles and open'during the entire KNIT cycle. In this embodiment of the invention, the operator will load the dryer as previously described, shut the access door to close the door. switch 30 and rotate the controller 12' to select the desireddrying cycle. Subsequent depression of the push to start button 13 initiates operation of the dryer -as described above with reference to circuitof FIG. 2.

Selection of the automatic drying cycle effects closure of the contact58in addition to closure of the contacts 17 and 18. Therefore, as the moisture sensing apparatus experiences sufficient voltage across the junction points 4,8'and S3 to maintain SCR 54 conductive, the timer motor will be prevented from operation due to the shuntingeffect of the contact 58 and SCR 54. Upon a decrease of voltage across the junction points 48 and 53 resulting from the clothesdrying out, SRC 54 will be rendered nonconductive and the timer motor will be permitted to operate throughthe remainder of the drying cycle.

Selection of the knit cycle of operation, however, causes contact 58 to close at a later time in the drying cycle 'so that stalling of the timer motor is prevented until closure of contact 58. If the fabrics are sufficiently dry when contact58 closes, the timer willcontinue to operate and complete the timing of the cycle. If the fabrics are still wet, the timer will be stalled until the fabrics aresufficiently dry, at which time the timerw'ill be energized to complete thecycle,

As' inthe previously. described embodiment of this invention,'contact' 59 is effective to expose the garments to a lower drying temperature. The switch contact 59 scope of our contribution to the art.

The embodiments of -the invention in whichan exclusive property of privilegeis claimed are defined as follows:

l. A control circuit for a clothes dryer including a programmer having an automatic cycle which is presettable to a plurality of selected degrees of dryness comprising first circuit means including said programmer, condition sensitive circuit means connected to said first circuit means for operating said programmer in response to detection of a condition indicative of a predetermined degree of dryness, and third circuit means connected to operate said programmerto a point a predetermined period priorto the end of said cycle regardless of detection of said condition by said condition sensitive circuit means, wherein the dryer has heating means for connection to an electrical supply, and wherein said first circuit means comprises a timer motor for connection to said electrical supply and adapted to advance said programmer when energized, said conditionsensitive circuit means is connected in parallel with said timer motor and operative to shunt said timer motor and prevent operation thereof, said third circuit means includes a first switch connected in series with said condition sensitive circuit means and operable to open said parallel connection to prevent shunting of said timer motor, a pair of thermostatic switches connected in circuit with said heating means and adapted to detect heating of the articles being dried, one of said thermostatic switches operable to open at a lower temperature than the other thermostatic switch, and a second switch connected in circuit with said pair of thermostatic switches for selective connecting one or the other of said thermostatic switches in control of .said. heating means.

2. A control circuit according to claim 1, wherein saidfirst and second switches are coupled for manual operation.

3. A control circuit according to claim 1, wherein said second switch is normally closed and connected in parallel with said one thermostatic switch.

4. In a control circuit a. clothes dryer including a programmer having an automatic cycle which is presettable to a plurality of selecteddegrees' of dryness, a timer motor connected between a pair of power leads and adapted to advance said programmer when energized,

a controlled conduction device connected in circuitwith said timer motor to render said timer motor inoperative when said controlled conduction device is in first circuit means including programmer means presettable to a plurality of selectedmoisture levels for providing operation of the dryer through a selected program, condition sensitive circuit means connected to said first circuit means for controlling operation of said programmer means in response to detection of moisture level conditions, and third circuit means connected to said condition sensitive means and being selectively presettable for selectively overriding said condition sensitive circuit means whenever a selected moisture level of the programmer means is less than a predetermined moisture level sensed by the condition means, one of said thermostatic switches operable to i open at a lower temperaturethanthe other thermostatic switch, and switch means connected in circuit with said thermostatic switches and operable to effect energization control of said heating means selectively by said one thermostatic switch whereby articles being dried are subjected to lower temperatures than when energization control iseffected by the other thermostatic switch.

' I t I II I! 

1. A control circuit for a clothes dryer including a programmer having an automatic cycle which is presettable to a plurality of selected degrees of dryness comprising first circuit means including said programmer, condition sensitive circuit means connected to said first circuit means for operating said programmer in response to detection of a condition indicative of a predetermined degree of dryness, and third circuit means connected to operate said programmer to a point a predetermined period prior to the end of said cycle regardless of detection of said condition by said condition sensitive circuit means, wherein the dryer has heating means for connection to an electrical supply, and wherein said first circuit means comprises a timer motor for connection to said electrical supply and adapted to advance said programmer when energized, said condition sensitive circuit means is connected in parallel with said timer motor and operative to shunt said timer motor and prevent operation thereof, said third circuit means includes a first switch connected in series with said condition sensitive circuit means and operable to open said parallel connection to prevent shunting of said timer motor, a pair of thermostatic switches connected in circuit with said heating means and adapted to detect heating of the articles being dried, one of said thermostatic switches operable to open at a lower temperature than the other thermostatic switch, and a second switch connected in circuit with said pair of thermostatic switches for selective connecting one or the other of said thermostatic switches in control of said heating means.
 1. A control circuit for a clothes dryer including a programmer having an automatic cycle which is presettable to a plurality of selected degrees of dryness comprising first circuit means including said programmer, condition sensitive circuit means connected to said first circuit means for operating said programmer in response to detection of a condition indicative of a predetermined degree of dryness, and third circuit means connected to operate said programmer to a point a predetermined period prior to the end of said cycle regardless of detection of said condition by said condition sensitive circuit means, wherein the dryer has heating means for connection to an electrical supply, and wherein said first circuit means comprises a timer motor for connection to said electrical supply and adapted to advance said programmer when energized, said condition sensitive circuit means is connected in parallel with said timer motor and operative to shunt said timer motor and prevent operation thereof, said third circuit means includes a first switch connected in series with said condition sensitive circuit means and operable to open said parallel connection to prevent shunting of said timer motor, a pair of thermostatic switches connected in circuit with said heating means and adapted to detect heating of the articles being dried, one of said thermostatic switches operable to open at a lower temperature than the other thermostatic switch, and a second switch connected in circuit with said pair of thermostatic switches for selective connecting one or the other of said thermostatic switches in control of said heating means.
 2. A control circuit according to claim 1, wherein said first and second switches are coupled for manual operation.
 3. A control circuit according to claim 1, wherein said second switch is normally closed and connected in parallel with said one thermostatic switch.
 4. In a control circuit a clothes dryer including a programmer having an automatic cycle which is presettable to a plurality of selected degrees of dryness, a timer motor connected between a pair of power leads and adapted to advance said programmer when energized, a controlled conduction device connected in circuit with said timer motor to render said timer motor inoperative when said controlled conduction device is in one conduction state, a gating circuit for said controlled conduction device including a capacitor and a plurality of moisture sensing electrodes, the improvement comprising a first, programmer operated, switch connected in parallel with a second manually operated, switch, said first and second switches being connected in circuit with said controlled conduction device so as to render said controlled conduction device incapable of rendering said timer motor inoperative when both said first and second switches are open. 